1. Field of the Invention
The present invention relates generally to ink cartridges. In particular, the present invention is directed towards ink cartridges which may be used in combination with ink jet printers.
2. Description of Related Art
A known ink jet printer is configured to dispense ink onto a sheet of paper to record an image on the sheet of paper. The known ink jet printer has a recording head. The recording head is configured to selectively eject ink from nozzles to the sheet of paper. A known ink cartridge is configured to be removably mounted to the ink jet printer. The ink cartridge has an ink chamber configured to store ink therein, and ink is supplied from the ink chamber to the recording head when the ink cartridge is mounted to the ink jet printer.
The ink cartridge has a movable member positioned in the ink chamber. The movable member is configured to pivot based on the amount of ink stored in the ink chamber. When the ink is consumed and the amount of ink in the ink chamber becomes less than a sufficient amount of ink, an end of the movable member moves from a first position at which the end of the movable member is detected by a detector e.g., an optical sensor, to a second position at which the end of the movable member is not detected by the detector. Consequently, whether the ink chamber has a sufficient amount of ink stored therein may be determined based on the position of the end of the movable member.
The movable member is submerged in ink when the ink chamber has an amount of ink which is substantially greater than a sufficient amount of ink. As the ink in the ink chamber gradually decreases, the movable member gradually becomes exposed above the surface of the ink. When the movable member is exposed from the surface of the ink, a web-shaped film of ink or a balloon-shaped film of ink may be formed between the movable member and inner wall of the ink chamber. The film may inhibit or restrict the pivotal motion of the movable member, and the end of movable member may not be detected accurately. For example, when the movable member attempts to pivot away from the surface of the ink, the film may draw the movable member towards the inner wall of the ink chamber.